648 [Proc. B.N.F.C, 



The constancy of the direction of glacial stria, throughout 

 wide regions, has long been regarded as a weighty argument against 

 the adequacy of submergence and floating ice to account for the 

 distribution of drifts ; and I should ask permission to mention 

 another conception which seems to me to militate against the 

 submergence theory. Take the case of chalk erratics known to 

 be carried up over the escarpment, westward into the Braid 

 Valley. If the submergence were adequate to float bergs over the 

 points where these fragments occur, we cannot suppose that they 

 could have been wrenched off by glaciers which yielded the bergs, 

 from the Chalk outcrop, several hundred feet lower down. 



From such reasonings, I trust the standpoint here taken, 

 that of continuous ice-sheets moving in various directions at 

 different times, will be deemed admissible, if only as a working 

 hypothesis. 



One other point of a general bearing may here also be 

 mentioned, namely, the occurrence at Portstewart and elsewhere 

 in North Derry, of granite blocks of striking resemblance to 

 Barnesmore granite. One of these, 3 feet by 3 feet 6 in. in 

 diameter, I have met on the slope just below Heathfield House, 

 north of Garvagh. I do not think anyone will contend for their 

 transference by an ice sheet so far eastward, from Barnesmore 

 across formidable ridges ; and carriage by floating ice over sub- 

 merged land requires the supposition of marine currents towards 

 the ice-bound coast of a continent, or towards an archipelago of ice- 

 covered islets and ice-flows. I prefer to think that these erratics 

 have come either from Scotland or from a submerged source to 

 the north of Ireland. 



For many years I have ventured to hold — 



1 st. — A west by south ice-flow from Scotland, as that 

 representing the oldest and greatest period of ice- 

 accumulation. 



